I let someone other with more experience of forwarding ports answer your first question.
To your second question, there are plenty of excellent VC:MP server mIRC scripts here
. In VC:MP, though, the commands are not formatted like /command, but either !command ot /c command. At least GUS have the possibility to register+login, stats, money etc., im not 100% sure about the others. If you have some experience with mIRC scripting and want to build your script yourself, VRocker's admin script seems quite good base for a new script, it has a lot of functions and callbacks in it.